Study On Low Concentration Ammonia Adsorption By Substrates And Its Adsorption Mechanism

Constructed wetland systems as an effective way to improve eutrophic water body have been applied extensively, but the choice of wetland-substrates is singleness which leads to the low removal rate of ammonia. Simulative experiments were carried out to effective NH₃-N removal material from natural and different modified clinoptilolites, ceramisite, vermiculite and fly ash. The results show that the highest ammonium adsorption efficiency was achieved by clinoptilolite and modified clinoptilolite. Ceramisite, modified ceramisite, natural and modified vermiculite were not suitable to dispose ammonium ions from synthetic aqueous solutions. Adsorption efficiency of ammonium ions for fly ash was improved by the modified technology. The highest ammonium adsorption efficiency was achieved by salt modified technique to clinoptilolites and ceramisite, but the highest ammonium adsorption efficiency was achieved by alkali modified technique to vermiculite and fly ash. The adsorption capacity of natural and modified clinoptilolite could increase when the temperature increased appropriately, but make against the rest of three substrates. The best pH range of the four natural and modified substrates to ammonia nitrogen was about the neuter deflection alkalescence. The ammonia nitrogen adsorption capacity was the least at strong acid (pH=2) and strong alkali (pH=13). The ammonia nitrogen had not been adsorbed by natural fly ash at the pH range of 2 to 13.The experimental results of mixed substrates adsorption show that the ammonium and phosphate ions compete against each other to the adsorption point in substrates. So the ammonium adsorption capacity for the mixed substrates containing clinoptilolite is higher than other mixed substrates, but is less than single clinoptilolite. The phosphatic adsorption capacity is relatively higher in the mixed substrates containing vermiculite. The desorption results show that the desorption amount of ammonium and phosphate are less than the adsorption amount to all study substrates. The solution of adsorption presents acidity for all groups, the solution of desorption enhances acidity than the adsorption solution.The mixed groups of clinoptilolites & ceramisite and clinoptilolites & vermiculite could remove nitrogen and phosphorus contamination, and the effect was better for the latter. The latter surfers much more oxidative stress compared with the fore and self-restoration capability is also much better than the fore.